1. Field of the Invention
The present invention relates to a PLC maintenance support device and a PLC maintenance support program, and more specifically relates to a PLC maintenance support device and a PLC maintenance support program used in an activation operation and a maintenance operation of a system including devices controlled by a PLC.
2. Description of Related Art
Systems that include devices (controlled devices) controlled by a programmable logic controller (PLC) sometimes cannot provide an expected operation. Therefore, to check the connection state of a signal cable, a method in which the voltage of a signal cable terminal connected to the controlled device is measured and compared with a value within the PLC is known (for example, Japanese Patent No. 3713387, hereinafter referred to as “patent document 1”). Also, as a part of the checking operation, a method in which while an output signal of the PLC is temporarily and forcefully turned on or off, the operation of the controlled device is checked, is known (for example, Japanese Patent No. 3161487, hereinafter referred to as “patent document 2”).
In a general method, the signal name of a signal cable the connection state of which is desired to be checked is identified from a mark tube having the signal name printed thereon, and the PLC displays a screen showing the state of the signal. Next, the voltage of the signal is measured by a tester, and compared with the state (on or off) of the signal in the PLC. Furthermore, as for an output signal, while the signal is temporarily and forcefully turned on or off by operating the PLC, an operation result is checked. This checking operation must be performed a number of times in order to check signals one by one, until an expected operation is obtained, thus causing a deterioration in efficiency.
Patent documents 1 and 2 disclose devices that improve efficiency in the connection checking operation of the PLC. However, the inventions of these documents cannot check the connections of input signals. Also, as for output signals, the connections of the output signals cannot be checked, unless the correspondences between signal assignments of the PLC and the devices connected through the cables are identified beforehand.